The invention relates to a hydraulic floor jack. The inventor of the present invention is fully involved with lifting devices, particularly including a two-part system. The two part system is inherently safer to use than a conventional floor jack to elevate a vehicle and which then requires the user to crawl under the vehicle to place a conventional jack stand adjacent to the elevated conventional floor jack to support the load. The inventor of the present invention is a pioneer of the two part jacking system and holds numerous patents related to this technology.
Briefly, the two part jacking system consists of a mobile hydraulic power unit having a flat front base and extendable lift arms; and a separate mechanical jack stand that can be secured within the front base of the power unit. The jack stand is elevated by extending the lift arms of the power unit, and locked by an integral ratchet locking mechanism. An example of the two part jacking system describing the power unit is shown in U.S. Pat. No. 7,420,148 (see FIGS. 1 and 9); and an example of the jack stand is also shown and described (see FIGS. 2-8).
The present inventor developed a “bridge” lifting plate positioned to bridge between the forward ends of the lift arms and adapts the power unit to function as a hydraulic floor jack. This adaptation was employed when all of the jack stands were in use, to more fully utilize the power unit for an additional project as a floor jack.
The use of the bridge with the power unit acting as a floor jack is best utilized with a safety mechanism to lock the elevated lift arms in position, in the event of any decay of hydraulic pressure while elevated. The pursuit of such a safety device for the power unit has led the present inventor to this unique solution to a long felt need for an automatic locking lift arm safety mechanism for the hydraulic floor jack.
A search for related prior art disclosed several old and simple devices. U.S. Pat. No. 5,984,270 by Hussaini et al, discloses a conventional floor jack including lift arms and a frame with pairs of lateral apertures therein. When the jack is elevated, a pin is manually placed under the lift arms and in the apertures, to support the lift arms in the event of any loss of hydraulic pressure.
U.S. Pat. No. 5,221,073 by Shockley discloses a conventional floor jack including lift arms and a frame with a series of opposing pairs of lateral notches in the upper side flanges of the frame. As the lift arms are raised, a bar is manually positioned under the lift arms and into one of the pairs of notches, to support the lift arms in the event of any loss of hydraulic pressure.
U.S. Pat. No. 2,998,224 by Reisig discloses an air-operated floor jack including lift arms and a frame with an air cylinder. The air cylinder has a ram with teeth on the upper surface that is engaged by a pawl pivotally attached to the top of the air cylinder. The pawl locks the elevated lift arms, until a lever is manually pulled to release the pawl, and the lift arms can then be lowered.
The prior art devices do not disclose or suggest a safety device for a hydraulic floor jack that automatically locks the lift arms in position when they are elevated; and which automatically un-locks lift arms when they are to be lowered.
It is an object of the present invention to provide a hydraulic floor jack having a safety mechanism that is reliable and durable that automatically locks the lift arms in position when they are elevated, and which is automatically releases with the control knob when the lift arms are to be lowered.